Wireless telecommunications capabilities have grown tremendously in recent years, and wireless device use has permeated into almost every sector of business and daily activity. As wireless communication expands, the demands placed upon the reliability of wireless technology increase. Accordingly, the complexity of wireless technology has grown exponentially. Wireless communications networks operate at ever-increasing bandwidths and over broadening frequency ranges. For example, in cellular networks Specialized Mobile Radio Service (SMR) can be implemented in the 800 MHz band or 900 MHz band and Personal Cellular Service (PCS) can operate in the 1900 Mhz band. Additionally, wireless local area network (WLAN) communication operates over high frequency bands, such as the 2.4 GHz and 5 GHz public spectrum bands for IEEE 802.11 Standards. Signaling bandwidths are also increasing to enable higher data rate applications.
These wireless communication networks are subject to a number of RF propagation impairments that increase in scale as the transmission bandwidths increase. One significant problem in wireless communication is due to the detrimental effects of polarization shifting on a wireless transmission signal. Propagation problems can include interference with multipath reflections off nearby objects. Furthermore, many transmit and receive sites for wireless communication devices are not in a direct line-of-sight (LOS). As such, wireless signals are subject to significant degradation due to polarization mode dispersion effects. These detrimental effects are increasingly present in high frequency implementations.
Discussion in the prior art regarding polarization behavior has been focused on diversity gain, polarization component delay and loss, and depolarization effects. Some prior art wireless telecommunication systems have attempted to implement polarization diversity architectures to combat the detrimental effects of polarization-sensitive fading. Some prior art systems rely upon limited cross-polarization discrimination techniques to attempt to characterize the polarization effects in a particular channel. Additionally, some prior art systems have relied upon calculations of delay spread and path loss in attempt to accurately characterize polarization-based channel impairments.
Conventional prior art wireless communication systems have been unable to accurately adapt to model polarization impairments over a wireless signal path particularly when the multipath delay-bandwidth product is sufficient to induce polarization mode dispersion, which is a spread of the signal polarization state as a function of frequency. Accordingly, conventional prior art wireless communication systems have been unable to efficiently and effectively reduce the degradation in signal reception caused by polarization mode dispersion and polarization dependent loss. Therefore, it would be advantageous to provide an apparatus and method of adaptive polarization transmission to reduce the impact of polarization mode dispersion.
Additionally, it would be advantageous to provide an apparatus and method for efficiently and effectively reducing deleterious effects from polarization impairments on a wireless transmission signal.
Additionally, it would be advantageous to provide an apparatus and method for estimating an adaptive polarization response for the transmission of a signal through a polarization-impaired wireless transmission signal path.
Additionally, it would be advantageous to provide an apparatus and method to mitigate polarization dependent loss.